Metal sounding board for pianos



Jan. 2, 1923.

F. FRANKEL;

METAL-SOUNDING BOARD FOR Pumas.

FILED MAR. 24, I920.

Patented Jan. 2, 1923.

UNITED STATES PATENT OFFICE.

FRIDOLF FRANKEL, OF STOCKHOLM, SWEDEN.

METAL SOUNDING BOARD FOR PIANOS.

Application filed March 24, 1920.

To all whom it may concern:

Be it known that I, FniooLr FRANKEL, a subject of the King of Sweden, residing at Stockholm, in the Kingdom oi Sweden, have invented a new and useful Improvement in Metal S ding Boards for Pianos, of which the following a specification.

The present invention relates to an improvement in metal sounding boards for pianos, has for its purpos to increase the resoundi, power of such sounding-boards. The have tion is broadly characterized by this that the edge portions of the soundinghoard are contracted or shortened relativ ly to the portions within said edges. In this manner a cup-shape or convexity of the sounding-b0ard is obtained, and simultaneously there is produced stress or tension in the board, which in turn produces an increased resounding power.

In the accompanying drawing an enibodiment 0' the intention iilustrated. shows the front side of the soundingdioard, Fig. 2 is section on the line Ili-ll in 1, and F. 3 is a section on the line ill-Ill. in Fig. 1, i i, 2 and 3 both showing the curvature or convexity of the heard in an e gerated way.

in the sounding-board 1 which is formed of a whole continuous metal plate, there are formed corrugations or bent-up fields or ribs E2 which have an approximately U-shaped or ii-shaped cross section. The said ribs 2 preferably project above the front side of the sounding-board 1, to which sioe the bridge or bridges 5 over which the strings are retched, are secured, as it has been found that the resounding power of the sounding);- board is increased if said bridge or bridges 5 hear directly against the ribs 2.

The sounding-board 1 is attached to the fastening rim 3 by soldering or in any other Serial No. 368,230.

suitable manner. Vhen attaching the board 1 to the rim 3 each rib "2 is squeezed or pressed together in suitable manner at its ends a at the edges of the sounding-board. so that the cross section oi said ends 4r. of the ribs becomes slightly narrower than that of the intermediate portions of the ribs, shown to the left in Fig. 2. in this manner the e ges oi the sounding-hoard will. oi course become contracted or shortened, and there will therefore be produced a certain tension in the inner portions of: the board. (living to the contraction of the edges the sounding-board will of course also be convex or cup-shaped to a certain extent with a resultant increase of its capability of supporting the strings. Said capability may bdstili more increased by pressing or haininerins the middle portion in the direction towards the strings by which operation the soundin93- board becomes still more convex or con shaped.

I claim:

1. A metal sounding-board for pianos provided with bent up ribs having approximately V-shaped cross section and projecting ahove the front side of the sour ng-board each of said ribs being pressed together at its ends at the edges oi? the soundiiig-board. for the purpose of producing contractions of the edge portions of the sounding-board.

2. A. metal soun din f"-l)()21l(l for pianos consisting of a continuous metal plate provided with bent-up ribs having approximately V-shaped cross section and projecting above the "front side of the sour.ding-board, each of ribs being pressed together at its ends at the edges of the soundingdioard, for the purpose of producing contractions of the edge portions of the sounding-board FRIDOLF FRANKEL. 

